Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C31/00—Saturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
  • C07C31/18—Polyhydroxylic acyclic alcohols
  • C07C31/20—Dihydroxylic alcohols

Definitions

• This invention relates to a process for the preparation of ⁇ , ⁇ , ⁇ ', ⁇ '-tetramethyl-phenylene-biscarbinols, which will hereinafter be referred to as biscarbinols, with a low hydroperoxide and ketone content by the oxidation of diisopropyl benzenes with air or oxygen at elevated temperatures in the presence of strong aqueous alkalis.
• Biscarbinols are important starting materials for the preparation of bisphenols and aromatic diamines which in turn are used for the production of linear thermoplastic polycondensates, for example polycarbonates, polyurethanes, novalaks or resols.
• Highly alkylated bisphenols are very effective stabilisers for polyurethanes.
• the biscarbinols When used for these purposes, the biscarbinols must be exceptionally pure. Contamination with hydroperoxides and carbonyl compounds must be particularly avoided. The latter are formed in side reactions during the oxidation process and consist mainly of acetophenone derivatives. If these impurities are present in quantities of only a few percent by weight, they have a harmful effect on the properties of the resulting polycondensation products. Resols and resites, for example, cause discolourations and a deterioration in the mechanical properties. Complicated purification processes involving considerable losses are necessary for removing these unwanted byproducts. The purification also results in a loss of biscarbinol yield.
• 1,253,692 to carry out the oxidation of diisopropyl benzenes at alkali concentrations of at least 40 percent by weight, preferably 60 percent by weight, based on the aqueous phase and about 20 percent by weight, preferably 40 percent by weight based on the organic phase. This measure does in fact reduce the hydroperoxide and ketone content.
• the present invention therefore relates to an improved process for the preparation of ⁇ , ⁇ , ⁇ ', ⁇ '-tetramethyl-phenylene-biscarbinols by the oxidation of optionally substituted diisopropyl benzenes with air or oxygen at elevated temperatures in the presence of aqueous solutions of strong alkalis, the improvement comprises carrying the oxidation out with a monocarbinol and/or biscarbinol content of at least 52% by weight in the organic phase and a concentration of alkalis of at least 8% by weight, based on the aqueous phase and 1 to 10% by weight, based on the organic phase.
• the gas used for oxidation can be fed in at such a rate that all the oxygen is used up and the exhaust gas is therefore free from oxygen and hence non-explosive. If desired, however, oxidation may also be carried out with an oxygen excess.
• Suitable starting compounds for the process according to the invention are m- and p-diisopropyl benzene, ⁇ -hydroxy-m- and -p-diisopropyl benzene and mixtures of these compounds.
• the alkalis used may be sodium hydroxide and potassium hydroxide.
• the process may be carried out discontinuously, but is particularly suitable for continuous operation because the most suitable reaction conditions for the invention can then be adjusted more easily.
• the reaction temperature employed is preferably between 75° and 145° C, more preferably between 90° and 120° C.
• Oxidation is preferably carried out at a pressure of from 1 to 50 bar. No significant improvement is obtained by employing pressures above 50 bar.
• Alkali is used up by the oxidation byproducts such as carbon dioxide and carboxylic acids during oxidation and must be replaced, preferably in a concentrated form since it gets diluted to the required concentration by the water present and the water formed in the reaction.
• the alkalis may be added in a concentrated, solid or dilute form.
• the supply of air or oxygen into the reaction mixture is carried out by known methods, either using frits or inlet tube in bubble columns or with the aid of stirring, preferably with the use of gasification stirrers which ensure efficient distribution of gases in liquids.
• Oxygen is introduced into 1500 g of a mixture of 476 g of fresh diisopropyl benzene, consisting of about 40% of p- and about 60% of m-diisopropyl benzene and 1024 g of a mixture of 216 g of diisopropyl benzene and 808 g of ⁇ , ⁇ '-dimethyl-isopropyl phenyl carbinol which has been isolated from a previous batch and 390 g of a 35% sodium hydroxide solution at 100° to 110° C.
• a gasification stirrer in the form of a cross blade agitator with a hollow axial shaft rotating at about 500 to 600 revs per min is used for introducing the oxygen.
• the organic phase contains 15% of diisopropyl benzene, 41% of monocarbinol, 44% of biscarbinol and 0.1% each of acetophenone derivatives and active oxygen.
• the aqueous phase contains 15% of sodium hydroxide. The remainder is neutralised with silicic acid (from the glass) and oxidation byproducts. The quantity of alkali is therefore about 4% by weight, based on the organic phase.
• the yield of biscarbinol is 91% of the theory, based on the degree of conversion of the hydrocarbons.
• Diisopropyl benzene is continuously oxidised with air to biscarbinol in a pressure reactor equipped with a hollow shaft gasification stirrer. The temperature is 100° C and the pressure 20 bar.
• the concentration of the various components in the organic phase when a steady state has been reached is 30% of diisopropyl benzene, 51% of ⁇ , ⁇ -dimethyl-isopropyl phenyl carbinol, 19% of biscarbinol and 0.2% of each of acetophenones and active oxyen.
• the aqueous phase has an NaOH content in the steady state of 25%.
• the proportion of organic phase to aqueous phase is 1 : 0.165, which corresponds to about 4% of sodium hydroxide based on the organic phase.
• a mixture of 194 g of biscarbinol (1 mol), 752 g (8mol) of phenol and 10 ml of 85% phosphoric acid are heated to a reaction temperature of 80° C at reduced pressure with stirring while the water of reaction is distilled off. After a reaction time of 2 hours, all the water has been removed and a pressure of 25 Torr has been reached. After a further 6 hours, 8.8 ml of concentrated sodium hydroxide solution are added and phenol is distilled off at 210° C and 10 Torr. 278 g of a clear, light-coloured hard resin which has a phenolic hydroxyl content of 7.5 and a colour index number of 0 is obtained.
• the colour index number was taken from the iodine scale and determined on a 50% solution of the resin in n-butanol.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (6)

• 1974
  • 1974-10-04 DE DE2447346A patent/DE2447346C3/de not_active Expired
• 1975
  • 1975-09-29 US US05/617,381 patent/US4044058A/en not_active Expired - Lifetime
  • 1975-10-01 GB GB40121/75A patent/GB1500330A/en not_active Expired
  • 1975-10-02 JP JP50118313A patent/JPS5915891B2/ja not_active Expired
  • 1975-10-02 IT IT51608/75A patent/IT1056134B/it active
  • 1975-10-02 CA CA236,908A patent/CA1063622A/fr not_active Expired
  • 1975-10-03 FR FR7530410A patent/FR2286807A1/fr active Granted
  • 1975-10-03 NL NL7511677A patent/NL7511677A/xx unknown

Patent Citations (6)

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